[ntp:questions] Re: Questions about using GPS receiver to synchronize PowerBook G4
bg at lysator.liu.se
Sun Mar 27 19:30:57 UTC 2005
Ningyu Liu <nul105 at psu.edu> writes:
> I need accurate timing (~1 ms) for an outdoor experiment. I have an
> Apple PowerBook G4 and plan to use a GPS receiver to synchronize its
> time. I have several questions about this issue.
> 1) Is the PPS signal necessary for the time synchronization? Can I get
> 1 ms accuracy from the NMEA message alone?
You will most likely need the PPS. NMEA messages will often "jump
around" depending on processor load in the receiver, no of satellites
> 2) Since the PowerBook G4 doesn't have a RS-232 port, can I use a USB
> GPS receiver or a RS-232 GPS receiver with a USB adaptor?, or maybe a
> bluetooth GPS receiver?
To get the NMEA, yes I think that would work. The problem is getting
the PPS pulse onto a pin that can trigger an interrupt -- status pin
on serial port or the ACK pin on an parport.
> 3) Is there any other way to synchronize this laptop?
Does your laptop have an PCMCIA/PCCARD bay? Try getting a serialport
PCCARD. I have used one from Socket, but not for timing
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